This invention relates to an improved arming unit and more particularly to an arming unit which positively retains the arming wire within the arming unit to thereby prevent arming unit preloading and which also incorporates an arming wire self-cleaning feature.
In the utilization of ordnance stores such as bombs and rockets it is highly desirable to provide means by which the store may be rendered completely safe and not subject to accidental ignition. This is generally accomplished by providing an arming device which when energized operates to orient the parts of the fuze and the explosive portion of the missile only at a time determined by the requirements of the situation, preferably immediately prior to the release of a missile during an attack. If the missile is armed substantially prior to its utilization, a substantial danger exists that the missile will be accidentally fired or ignited; this condition would be extremely hazardous to the personnel handling the ordnance apparatus and the crew of the aircraft. Use of permanently armed missiles would also greatly complicate the care required in handling and storing explosive missiles.
It is desirable, therefore, to employ a device which selectively controls the arming of explosive missiles so that bombs carried beneath an aircraft may have an arming wire extended therefrom which is retained in fixed relationship to the aircraft. Thereby, upon release of the missile, the arming wire is withdrawn from the missile fuze placing the various parts thereof in condition for firing at the critical time or under the critical conditions of impact or proximity.
Furthermore, it is desirable that such arming apparatus be capable of remote control by a pilot, or the like, to selectively release the arming wire, permitting the discharge of a missile in an emergency without conditioning the various parts thereof for firing. For example, it is sometimes desirable or necessary to discharge missiles while over friendly territory or a portion of an airfield.
Arming units are electromechanical solenoid actuated devices which determine whether a conventional fuzed weapon will be dropped in an unarmed (safe) condition or in an armed condition. Arming units are adapted to be secured to a bomb rack or weapon suspension equipment which is located, for example, on the underside of an aircraft wing.
A widely used prior art arming unit comprises a solenoid actuated electromechanical device which is contained within an aircraft's weapon suspension equipment and which is used to arm or safe the mechanical fuzing of conventional weapons. A suspended weapon is prepared for functioning by inserting an arming wire's swivel loop into the arming unit's restrictive slot and by attaching the other wire end to the weapon's mechanical fuze and restraining frictional safety clip. The weapon may be armed by energizing the arming unit's 28 volt DC solenoid to retain the swivel loop within the arming unit and ultimately pull the arming wire out of the safety clip and fuze at the time when the weapon is separated from the aircraft. A weapon is released in the unarmed (safe) condition by not energizing the arming unit which permits the unretained arming wire to drop with the weapon and its associated fuze and safety clip.
With the relatively low speeds of 1940 vintage aircraft arming units with arming wire holding forces of two pounds and release forces of eight pounds were adequate for intended service. However, high performance aircraft used in current service create air turbulences and high arming wire airloads in excess of the holding forces for which these units were intended. Consequently the holding forces were increased to a range of ten to twelve pounds.
Even with the increase in arming wire holding forces an undesirably large number of arming units were observed to function improperly, i.e., an unarmed weapon was dropped when it was intended to drop an armed weapon. Prior art arming unit malfunctions were found to be caused by a variety of factors, such as:
a. preloading of the arming wires by aerodynamic loading, tight arming wire rigging or both;
b. camming of the arming wire swivel loops in the arming unit slot;
c. side loading of the arming wire caused by off-centerline arming wire routing, rolling of the weapon upon its release, non-vertical release of the weapon or combinations of these;
d. the difficulty of maintaining a safe jettison force range under fleet operational conditions; and
e. arming unit housing failures which occur during normal operations.
In addition, the relatively high safe jettison release force (8-10 pounds) which the prior art arming unit exhibits allows the undesirable retention of the arming wire after an armed weapon has been released. Retained arming wires flail about in the aircraft's windstream causing damage to the aircraft wings and appendages.